Results

          Looking at the species suitability map from Maxent (Figure 5) it is clear that the southern mountains of the study area are the ideal habitat for the Clark’s nutcracker. However, the interesting results come from comparing the suitability map for the Clark’s nutcracker to the range of the whitebark pine (Figure 9). This illuminates multiple things. Firstly, the two species clearly share much of the same habitat, an obvious outcome of their relationship (noted in the background section). Secondly, it appears that the whitebark pine range already goes further north than the areas of the highest “probability of suitable conditions” (Phillips, 2017 p. 113) for the nutcracker. However, the areas of moderate “probability of suitable conditions” (Phillips, 2017 p. 113) for the nutcracker go far beyond the extents of the pine’s current range, offering some hope that the bird will be able to move northward with whitebark pine planting efforts. It is worth noting here that Maxent shows the fundamental niche, that is, where the species could be found based on the factors the model was given. It does not consider other factors such as predators, other competing species or distribution factors. Therefore, the realized niche for the Clark’s nutcracker is likely smaller than the fundamental niche displayed. 

          Comparing the whitebark pine range and the species distribution model for the Clark’s nutcracker, there is one area of distinct difference. The southernmost area of British Columbia between the Coastal and Rocky mountain ranges (the Kelowna and Kamloops area) is of high suitability for the bird, but not the tree (Figure 9). Likely, this is partly because whilst both prefer the mountainous habitat, the whitebark pine is much more rooted (shall we say) to that environment, whereas the nutcracker must descend to lower elevation for some reason (even if just to move between mountain ranges). Additionally, however, this may be due to the bias of the large human population present in this area contributing to the occurrence sighting data, despite the use of a bias file. The same appears to be true for the southernmost area of Alberta, near the foothills of the Rocky Mountains (Figure 9). 

         The performance of the Maxent model appears quite good (Figure 8), indicating that the points are clearly not randomly distributed in the landscape. Although, “[i]t is important to note that AUC values tend to be higher for species with narrow ranges, relative to the study area described by the environmental data. This does not necessarily mean that the models are better; instead this behavior is an artifact of the AUC statistic”  (Phillips, 2017 p. 113). This may be, at least partially, the case for this model. 

          Although the model indicated that temperature seasonality had the strongest contribution to the model (Figure 7), because we did not check the correlation between layers, any assumptions about the relative importance of the bioclimatic variables should be done carefully. 

          For those interested in a more nuanced look at the suitability of habitat for the Clark’s nutcracker, the response curve data offer insight into how each environmental variable impacts the suitability for the nutcracker (Figure 6).